This invention relates to struts having releasable fastener means, and more particularly to strut devices of the type having telescoping inner and outer tubular members arranged to be releasably secured to one another in predetermined, fixed positions.
Prior devices of this type have included inner and outer telescoping members wherein the outer member carried arcuate locking dogs in radially extending slots, together with an external sleeve slidable thereon and having an internal camming shoulder engageable with the dogs so as to effect advancing and retracting movement of the latter into grooves or recesses in the inner tubular member. Such a telescoping strut is described in U.S. Pat. No. 3,442,541, issued May 6, 1969 to Joseph R. Metz. The present invention involves improvements to the construction illustrated in FIGS. 6-12 of this patent.
While the devices disclosed in the above mentioned patent operated in a satisfactory manner, there was no provision for positively locking the external sleeve in its advanced position (illustrated in FIG. 6 of the patent) with respect to the outer tubular member. Instead, complete reliance was placed on the ability of the spring to maintain the sleeve in the advanced (locking) position. It has been found that under conditions of substantial tensile or compressive forces applied to the members, there is a possibility of inadvertent release of the strut in the event that the sleeve is accidentally bumped, jarred, or otherwise handled. Due to the large forces which were often involved, such inadvertent releasing of the strut could have undesirable consequences, such as injury to personnel, damage to equipment, etc. It has been found that a more substantial locking arrangement was necessary in order to provide more reliable and foolproof functioning.